SETTLING AND RISING VELOCITY OF A SPHERICAL PARTICLE IN HOMOGENEOUS TURBULENCE

Abstract

The average settling and rising velocity in homogeneous turbulent fields of a spheri- cal particle have been examined. The velocity field of homogeneous isotropic turbulence is simulated by Kraichnan's technique. Both experimental and numerical results are shown. From experimental and numerical results, it is found that both light and heavy particles tend to be delayed by relatively weak turbulence. The results also show an increase in the average settling velocity when turbulence intensity is relatively strong. In the experiments, the rising velocity for a light particle decreases greatly with increas- ing relative turbulence intensity. An decrease by a factor of 0.05 is observed in the grid turbulence. The increases and decreases in the simulation are small in comparison with those in the experiments.